_ Source: _Volume 60, Issue 1, pp 88 - 126 The dominant interpretation of Metaphysics Θ.8 commits Aristotle to the claim that the heavenly bodies’ eternal movements are not the exercises of capacities. Against this, I argue that these movements are the result of necessarily exercised capacities. I clarify what it is for a heavenly body to possess a nature and argue that a body’s nature cannot be a final cause unless the natural body possesses capacities that are exercised for (...) the sake of its nature qua form. This discussion yields a better understanding of what capacities are, what explanatory work capacities do, and what it is to possess a nature. (shrink)